Hydrogen in storage systems is typically held at pressures ranging from 20 to 875 bar. However, hydrogen is delivered to a user, e.g. a fuel cell, at lower pressures in the range of 6 to 10 bar, for example. In order to efficiently deliver the hydrogen to the user at a desired pressure, a pressure regulator is needed. Accordingly, there are multiple pressure regulators that may be used. Where the pressure regulator includes a piston for sensing and regulating pressure, seals are required. In certain applications, such as fuel cell systems for example, seals are required to withstand temperature variations in a range of −80° C. and +85° C.
U.S. Pat. App. Pub. No. 2008/0011361 to Larson discloses a pressure regulator including O-ring seals formed from an elastomer. As described in Larson, an elastomer such as ethylene propylene rubber (EPDM) may be suitable for temperatures approaching −50° C. However, the temperature of the hydrogen travelling from a hydrogen storage system to a fuel cell can decrease to values as low as −80° C. Because of the lower temperatures, O-ring seals made of an elastomer are no longer effective.
It is well known to a person skilled in the art of pressure regulators that a seal may also be formed from a silicon material for application in low temperature environments. However, silicon is not an appropriate sealing material for use with hydrogen, as silicon does not have a desirable permeability and is pourous to hydrogen.
It would be desirable to have a pressure regulator for a hydrogen storage system, wherein the pressure regulator is adapted to efficiently operate at temperatures below −50° C., while minimizing the need for separate sealing elements and O-rings.